Add saloon-development skill documentation and streamline SaloonPHP guidelines.

[tdwesten]

Hi there,

The current Saloon Laravel boost guidelines are adding many lines to the main guidelines. I have simplified them into a new skill file.

[Cbrad24]

Might also be worth appending .md to the end of all the doc links. The documentation site supports it:
https://docs.saloon.dev/installable-plugins/laravel-integration.md

Also removes a lot of HTML bloat and token wasteage for AI agents.

Edit: Maybe this is the better option. There appears to be an llms.txt file that houses up to date links to the entire documentation in .md format.
https://docs.saloon.dev/llms.txt

[Sammyjo20]

Great PR, Thank you so much!